Susan Sontag (The Author)
This being a nonfiction essay, perhaps the most important character is the author herself. Having been thoroughly educated in philosophy, history, and literature, Sontag uses these sources as evidence to support her points in Regarding the Pain of Others, often to great effect. She has a pragmatic view of the world and an engaging, straightforward style of writing, making her essays enjoyable and informative. Her role as a political activist is also evident in her writing; instead of sitting back and philosophizing, she is more than willing to do something about the problems she poses, and that enthusiasm comes through in her writing.
Virginia Woolf
One of the most important writers of the 20th century, Virginia Woolf was a modernist author who significantly contributed to the world of literature through her use of the stream-of-consciousness technique, along with her many nonfictional works. In Regarding the Pain of Others, Sontag takes passages from Woolf's book Three Guineas, evaluating her pacifist standpoint and offering critiques to her argument against the Spanish Civil War.
Ernst Friedrich
As an example of the use of war photography to shock the public into action, Sontag references Krieg dem Kriege! (War Against War), a collection of photographs accompanied by explanatory text composed by German activist Ernst Friedrich during the First World War. These photographs - in turn stunning, horrifying, and depressing - achieved their intended effect, especially the section entitled "Faces of War," in which were depicted 24 close-up pictures of the scarred and wounded faces of soldiers.
Robert Capa
A well-known and admired Hungarian-American war photographer, Robert Capa is considered by some to be the best war photographer in history. His coverage of the Spanish Civil War - especially the shocking photograph called "Death of a Republican Soldier" - elicited much attention, and Sontag often references Capa as an example of how war photography can be effective, as well as a near-perfect example of how it is done stylistically. His work more or less represents the best of the genre, at least in Sontag's mind.